Flue gas temperature adjusting device for convection heating surface at tail part of WSC boiler

Abstract

The utility model relates to a WSC boiler tail convection heating surface flue gas temperature adjusting device which comprises a flag-shaped pipe heat exchanger water side bypass pipeline, a valve set, a first adjusting valve, a second adjusting valve and a third adjusting valve are arranged on the flag-shaped pipe heat exchanger water side bypass pipeline, one end of the first adjusting valve is connected with an inlet of a boiler water inlet collecting box, and the other end of the first adjusting valve is connected with an outlet of a boiler water outlet collecting box. The other end of the first adjusting valve is connected with the valve set and the second adjusting valve, the other end of the second adjusting valve is connected with the third adjusting valve, an outlet of the flag-shaped pipe upper header and an inlet of the economizer distribution header, and the water side bypass pipeline is connected with the heat supply network water return pipeline through the valve set. The utility model has the advantages that the pressure is set by the pressure sensor, the pressure is controlled to adjust the opening of the bypass valve, the pressure is limited to adjust the opening amplitude of the bypass valve, and the amount of water entering the heating surface of the boiler is controlled according to the closing temperature, so that the vaporization heat absorption intensity of the heating surface of the boiler can be controlled, and the vibration amplitude of the boiler caused by the reduction of water flow is reduced.

Description

Technical Field

[0001] The utility model relates to the field of SCR flue gas denitration of hot water boilers in the heating industry, and in particular to a flue gas temperature regulating device for a convection heating surface at the rear of a WSC boiler. Background Art

[0002] At present, for hot water boilers in the heating industry, if they need to meet the ultra-low emission limit of nitrogen oxides of 50mg / m 3 In order to meet the technical requirements of the denitrification system, the conventional technical means are: insert a medium-temperature catalyst in the temperature range of 350-420℃ on the heating surface at the rear of the boiler, spray urea, cause a reduction reaction, and reduce NOx to N2 and H2O. This is not a problem for conventional coal-fired units, but in the heating industry, the thermal load of the boiler changes with the outdoor temperature, resulting in a large fluctuation in the flue gas temperature at the rear of the boiler. Within the 2-4 hours required for the start and stop of the boiler, or when the weather turns warmer, the boiler is in the low-load, medium-low load operation range, and the reaction temperature of the catalyst layer set according to the design conditions is often lower than 350℃, affecting the stable operation of the denitrification system and failing to meet environmental protection requirements. Not only that, when the heating surface at the rear of the boiler is seriously dusted, resulting in deterioration of heat transfer, the originally suitable temperature range may become unsuitable due to the temperature increase exceeding the catalyst's upper temperature resistance limit of 420℃.

[0003] For the current boiler ultra-low emission transformation project, due to complex factors such as boiler operating fuel changes, aging, ash accumulation, and operating load deviating from the design value, how to choose the temperature range of 350-420°C has become a difficult problem in the industry.

[0004] One approach in the industry is to adjust the flue gas temperature by bypassing the flue gas. However, this adjustment method makes it difficult to set a huge isolation valve for the heating surface at the rear of the boiler. The high-temperature flue gas led out from the manhole door is limited by the size of the manhole door and the isolation valve cannot be set inside. The flow rate of the led flue gas is small, which has little effect on increasing the tail flue gas temperature. The extremely high dusty environment and flue gas temperature cannot be solved at a low cost for fans, dust removal equipment and dampers. Summary of the invention

[0005] The utility model aims to provide a flue gas temperature regulating device for the tail convection heating surface of a WSC boiler, which utilizes the water side bypass pipeline of a flag tube heat exchanger, does not need to modify the boiler water wall and the water wall ceiling, has no effect on the furnace body, and has low modification cost.

[0006] To achieve the above purpose, the utility model is implemented through the following technical solutions:

[0007] A flue gas temperature regulating device for a convection heating surface at the rear of a WSC boiler comprises a water-side bypass pipeline of a flag-tube heat exchanger, on which a valve group, a regulating valve 1, a regulating valve 2 and a regulating valve 3 are arranged, one end of the regulating valve 1 is connected to the inlet of a boiler water inlet header, the other end of the regulating valve 1 is respectively connected to the valve group and the regulating valve 2, the other end of the regulating valve 2 is respectively connected to the regulating valve 3, the outlet of a flag-tube upper header and the inlet of an economizer distribution header, and the water-side bypass pipeline is connected to a heat network return pipeline through the valve group.

[0008] It also includes a regulating valve four and a regulating valve five. The outlet of the economizer distribution header is connected to the inlet of the economizer collection header through a number of branch pipes one. The flue gas flows through each branch pipe from left to right from the side. The SCR reactor is arranged in the gap in the middle of the branch pipe bundle. An SCR catalyst is arranged in the SCR reactor. Each branch pipe one arranged upstream of the flue gas of the SCR reactor is provided with a corresponding regulating valve four at a position close to the economizer distribution header, and each branch pipe one close to the economizer collection header is provided with a corresponding regulating valve five.

[0009] The valve group is a cut-off valve and a check valve connected in series, and a pressure regulating bypass valve 1 is arranged at the outlet of the regulating valve 3.

[0010] A pressure regulating bypass valve 2 is provided at the inlet of the regulating valve 5. The flag tube upper header is used to collect the hot water of the flag tube bundle. The economizer distribution header is used to distribute the hot water from the flag tube upper header to the economizer tube bundle. The economizer collection header collects the hot water from the economizer tube bundle.

[0011] It also includes temperature sensors and pressure sensors. There are several temperature sensors and pressure sensors, which are used to detect the temperatures of the inlet flue gas duct of the boiler water inlet header, the inlet flue gas duct of the economizer distribution header, the front end of the SCR catalyst, and the economizer branch pipe arm. The pressure sensors are used to detect the valve front pressure of the regulating valve three and the valve front pressure of the regulating valve four.

[0012] The flag tube heat exchanger consists of a boiler water inlet header, a flag tube upper header, and a flag tube bundle connected between the boiler water inlet header and the flag tube upper header.

[0013] Compared with the prior art, the beneficial effects of the utility model are:

[0014] 1. The return water of the heating network is connected to the hot water boiler through the water-side bypass pipeline, without changing the boiler water-cooled wall and water-cooled wall ceiling, and has no impact on the furnace body;

[0015] 2. No need to introduce hot flue gas duct to adjust the flue gas temperature, which can reduce the project cost;

[0016] 3. Lead part of the flue gas out from the front of the flag tube heat collecting surface, reduce the amount of flue gas passing through the flag tube heat exchanger and economizer, reduce the heat exchange intensity, use mature and reliable steam-water valves, low failure rate and low maintenance cost;

[0017] 4. No need to short-circuit flue gas, which has little impact on the thermal efficiency of the boiler. At low load, although the heat absorption of the flag-shaped tube heating surface drops significantly, the tail economizer has an increased water flow, a lower water temperature, a larger temperature difference between flue gas and water, and an increased heat absorption due to the increased water flow, which saves coal consumption compared to the short-circuit flue gas method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the flue gas temperature regulating device for the rear heating surface of the WSC boiler.

[0019] Figure 2 This is the front view of the flue gas temperature control device for the rear heating surface of the WSC boiler.

[0020] Figure 3 It is a side view of the flue gas temperature regulating device for the rear heating surface of the WSC boiler.

[0021] In the figure: 1-valve group 2-regulating valve one 3-regulating valve two 4-regulating valve three 5-pressure regulating bypass valve one 6-regulating valve four 7-regulating valve five 8-pressure regulating bypass valve two 9-heat network return pipeline 10-water side bypass pipeline 11-flag-shaped tube upper header 12-economizer distribution header 13-economizer collection header 14-boiler water inlet header 15-boiler 16-economizer high temperature side 17-economizer tube bundle 18-first return elbow 19-flag-shaped tube low temperature side 20-flag-shaped tube 21-flag-shaped tube high temperature side 22-branch pipe two 23-branch pipe one 101-temperature sensor. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0023] A flue gas temperature regulating device for the tail convection heating surface of a WSC boiler 15 comprises a flag tube heat exchanger water side bypass pipeline 10, the flag tube heat exchanger is composed of a boiler 15 water inlet header 14, a flag tube upper header 11, and a flag tube bundle connected between the boiler 15 water inlet header 14 and the flag tube upper header 11, the flag tube bundle is used for the flue gas to flow through the flag tube bundle to transfer heat to the water in the bundle, so as to complete the heating of the water, a valve group 1, a regulating valve 1 2, a regulating valve 2 3, and a regulating valve 3 4 are arranged on the flag tube heat exchanger water side bypass pipeline 10, the valve group 1 is a shut-off valve and a check valve connected in series, one end of the regulating valve 1 2 is connected to the inlet of the boiler 15 water inlet header 14, the other end of the regulating valve 1 2 is respectively connected to the valve group 1 and the regulating valve 2 3, and the other end of the regulating valve 2 3 is respectively connected to the valve group 1 and the regulating valve 2 3. The ends are respectively connected with the regulating valve three 4, the outlet of the flag-shaped tube upper header 11, and the inlet of the economizer distribution header 12, and the water side bypass pipeline 10 is connected with the heat network return pipeline 9 through the valve group 1; the outlet of the economizer distribution header 12 is connected with the inlet of the economizer collecting header 13 through several branch pipes 23, and the flue gas flows through each branch pipe from left to right from the side. The SCR reactor is arranged in the gap in the middle of the branch pipe bundle. The SCR reactor is equipped with an SCR catalyst. The flue gas flows through the SCR reactor to complete the removal of NOx. Each branch pipe 23 arranged upstream of the SCR reactor flue gas is provided with a corresponding regulating valve four 6 near the economizer distribution header 12, and each branch pipe 23 near the economizer collecting header 13 is provided with a corresponding regulating valve five 7.

[0024] A pressure regulating bypass valve 1 5 is provided at the outlet of the regulating valve 3 4; a pressure regulating bypass valve 2 8 is provided at the inlet of the regulating valve 5 7; the flag tube upper header 11 is used to collect the hot water of the flag tube bundle; the economizer distribution header 12 is used to distribute the hot water from the flag tube upper header 11 to the economizer tube bundle 17; the economizer collection header 13 collects the hot water from the economizer tube bundle 17; there are several temperature sensors 101 and pressure sensors, which are respectively used to detect the temperature of the inlet flue gas pipe of the boiler 15 water inlet header 14, the inlet flue gas pipe of the economizer distribution header 12, the front end of the SCR catalyst, and the economizer branch pipe arm; the pressure sensors are respectively used to detect the valve pre-valve pressure of the regulating valve 3 4 and the valve pre-valve pressure of the regulating valve 4 6.

[0025] Working process:

[0026] In the process of regulating the flue gas temperature of the tail convection heating surface of the WSC boiler 15, the flag tube heat exchanger water side bypass pipeline 10 composed of the cut-off valve + check valve group, regulating valve 1 2, regulating valve 2 3, regulating valve 3 4 and pressure sensor and pipeline can realize the water flow control of the flag tube heat exchanger by adjusting the opening of each regulating valve. The specific contents are as follows:

[0027] 1) When the boiler 15 is started, the shut-off valve of the valve group 11 is fully opened, the regulating valve 12 is fully opened, the regulating valve 2 is closed, and the regulating valve 3 4 is fully opened. Low-temperature water enters the boiler 15 water inlet header 14 from the heat network return pipe 9 through the shut-off valve and the regulating valve 12. The boiler 15 water inlet header 14 distributes the hot water entering the header to the flag-shaped tube bundle. At this time, the flue gas of the boiler 15 will flow through the flag-shaped tube bundle to exchange heat. The water in the flag-shaped tube bundle is heated by the flue gas and then enters the flag-shaped tube upper header 11. The water in the flag-shaped tube upper header 11 flows through the regulating valve 3 4 and then enters the economizer distribution header 12. The outlet of the economizer distribution header 12 and the inlet of the economizer collection header 13 are connected through several branches. The pipe 23 is connected, the water in the economizer distribution header enters the economizer branch pipe, the flue gas flows through each branch pipe from left to right from the side, the low-temperature water is heated by the flue gas, and then enters the economizer collecting header 13; the SCR reactor is arranged in the gap in the middle of the branch pipe bundle, the SCR reactor is equipped with an SCR catalyst, and the flue gas flows through the SCR reactor to complete the removal of NOx; each branch pipe 23 arranged upstream of the SCR reactor flue gas is provided with a corresponding regulating valve four 6 at a position close to the economizer distribution header 12, and the fully open regulating valve four 6, and each branch pipe 23 close to the economizer collecting header 13 is provided with a corresponding regulating valve five 7, and the fully open regulating valve five 7.

[0028] 2) When the temperature of the flue gas measuring point arranged at the inlet of the SCR reactor is lower than 350℃, the regulating valve 23 will be opened slowly. At this time, a part of the low-temperature water directly enters the economizer distribution header 12 without passing through the flag-tube heat exchanger. The heat absorption of the flag-tube heat exchanger is reduced, and the temperature of the flue gas flowing out of the flag-tube heat exchanger is increased, thereby increasing the flue gas temperature at the economizer inlet, and then indirectly increasing the flue gas temperature at the inlet of the SCR reactor. When the regulating valve 23 is fully opened and still cannot increase the flue gas temperature at the inlet of the SCR reactor, the opening of the regulating valve 46 and the regulating valve 57 will be reduced synchronously until it is locked. The water flow upstream of the SCR reactor is reduced, the heat absorption is reduced, and the flue gas temperature is increased; when the regulating valve 46 and the regulating valve 57 are closed, the water temperature will rise because the water in the pipe is still involved in the heat exchange. In severe cases, violent vaporization will occur, causing the boiler 15 to vibrate and burst. Therefore, a pressure regulating bypass valve 28 is set at the inlet of the regulating valve 57. When the pressure exceeds the set value, the pressure regulating bypass valve is opened, and a pressure regulating bypass valve is set in front of the pressure regulating bypass valve. There is a pressure switch. When the pressure in the economizer pipe rises to the starting pressure, the pressure regulating bypass valve opens slightly to release the pressure. When the pressure drops, the pressure regulating bypass valve closes. This can control the boiling intensity of the water in the economizer branch pipe. When the water temperature reaches the vaporization temperature, the vaporization temperature is reflected by the displacement indicator arranged at the first elbow of the economizer branch pipe and monitored by the control system. The displacement indicator is related to the pipe wall temperature. When the displacement indicator exceeds a certain value, it means that the pipeline is over-temperature and the vaporization intensity is too large. At this time, the regulating valve four 6 and the regulating valve five 7 will be forced to open synchronously, and hot water will flow into the pipeline to cool it down.

[0029] 3) If the flue gas temperature still cannot reach 350°C, the opening of regulating valve 12 and regulating valve 34 will be reduced synchronously to reduce the water flow entering the flag tube heat exchanger until it is closed. The flue gas temperature at the outlet of the flag tube heat exchanger will increase, the flue gas temperature upstream of the SCR reactor will increase, and the flue gas at the inlet of the SCR reactor will increase; when regulating valve 12 and regulating valve 34 are closed, since the water in the tube is still involved in the heat exchange, the water temperature will rise, and in severe cases, violent vaporization will occur, causing the boiler 15 to vibrate and burst. Therefore, a pressure regulating bypass valve 15 is set. When the pressure exceeds the set value, the pressure regulating bypass valve is opened. A pressure switch is provided in front of the pressure regulating bypass valve. When the economizer tube pressure increases to the starting pressure, the pressure regulating bypass valve is slightly opened to release pressure. When the pressure decreases, the pressure regulating bypass valve is closed, which can control the boiling intensity of the water in the branch pipe of the flag tube heat exchanger. The flag tube heat exchanger is inside the furnace, so it mainly monitors the displacement of the boiler 15 water inlet header 14 to determine whether the tube bundle is overheated and the vaporization intensity is too large. Once overheated, the regulating valve 1 2 and the regulating valve 3 4 will be forced to open slowly, and water will be introduced to cool the pipeline.

[0030] The regulating valve is a shut-off valve with a certain regulating function, preferably a stop valve with a remote control function, and a shut-off valve and a check valve connected in series may also be used.

[0031] [Example 1]

[0032] See Figures 1 to 3A flue gas temperature regulating device and method for the tail convection heating surface of a WSC boiler is applicable to a hot water boiler 15 in which return water from a heating network enters the high temperature side of a flag tube 20 (also called a boiler tube bundle) and then enters the high temperature side 16 of an economizer. Three flue gas measuring points (referred to as 1# temperature measuring point 10111) are set on the inlet flue gas pipeline of a boiler water inlet header 14, three flue gas measuring points (referred to as 2# temperature measuring point 10112) are set on the inlet flue gas pipeline of an economizer distribution header 12, and three flue gas measuring points (referred to as 3# temperature measuring point 10113) are set in front of an SCR catalyst. The above temperature measuring points are flue gas condition input signals of a PLC control system; the temperature of the 3# flue gas measuring point 10113 is maintained at 320 In the temperature range of 450℃ to 450℃, an isolation and regulating valve (referred to as regulating valve 1 2) is set at the boiler water inlet header inlet after the boiler return water check valve and the cut-off valve group (referred to as valve group 1) to cut off and regulate the water flow of the boiler water inlet header inlet; a bypass is led out to the flag-type tube upper header outlet in front of the boiler water inlet header inlet valve, and an isolation and regulating valve (referred to as regulating valve 2 3) is set on the above bypass to cut off and regulate the above bypass water flow; an isolation and regulating valve (referred to as regulating valve 3 4) is set on the flag-type tube upper header outlet pipe to cut off and regulate the water flow of the flag-type tube bundle outlet, control the internal pressure and vaporization intensity of the flag-type tube, ensure that there is no overpressure in the flag-type tube 20, and adjust the bypass valve 1 through the pressure regulating bypass valve 1 5 is opened to control the vaporization intensity, reduce the risk of backflow of return water at a lower temperature, and reduce the impact of the vibration of the flag tube 20 caused by gas vaporization on the boiler; a pressure regulating bypass valve (referred to as pressure regulating bypass valve 15) is set before the regulating valve 3 4, and the outlet of the pressure regulating bypass valve 15 is connected to the regulating valve 3 4 to ensure that the flag tube 20 is not over-pressurized and the safe operation of the boiler is ensured; a pipeline is drawn out from the pipeline between the regulating valve 3 4 and the regulating valve 2 3 and connected to the inlet of the economizer distribution header 12, and the flag tube bypass water is sent to the inlet of the above-mentioned economizer distribution header 12. When the smoke temperature decreases, the bypass water starts to reduce the heat absorption of the heating surface at the rear of the boiler, thereby increasing the 3# smoke temperature value; at the outlet of the boiler economizer distribution header 12 An isolation and regulating valve (referred to as regulating valve 46) is set on the economizer branch pipe at the front end of the SCR catalyst inlet, which is used to control the water inlet flow of the above-mentioned economizer branch pipe; an isolation and regulating valve (referred to as regulating valve 57) is set on the economizer branch pipe at the front end of the SCR catalyst inlet of the boiler economizer collecting box 13, which is used to control the water outlet flow of the above-mentioned economizer branch pipe, control the internal pressure and vaporization intensity of the above-mentioned economizer branch pipe, reduce the risk of backflow of return water at a low temperature, and reduce the influence of the vibration of the economizer caused by gas vaporization on the boiler; a pressure regulating bypass valve (referred to as pressure regulating bypass valve 28) is set in front of the regulating valve 57, and the outlet of the pressure regulating bypass valve 28 is connected to the regulating valve 57 to ensure the safe operation of the boiler.Three flue gas measuring points (referred to as 1# temperature measuring point 101) are set on the flue gas duct at the inlet of the water inlet header, three flue gas measuring points (referred to as 2# temperature measuring point 10122) are set on the flue gas duct at the inlet of the economizer distribution header 12, and three flue gas measuring points (referred to as 3# temperature measuring point 10123) are set in front of the SCR catalyst. The above temperature measuring points are the flue gas condition input signals of the PLC control system; a remote displacement indicator (referred to as 1# displacement indicator) is set on the first return elbow 18 on the economizer branch pipe in front of the SCR catalyst at the outlet of the boiler economizer distribution header 12. The indicator is used to indirectly react to the wall temperature of the tube wall, and the signal is transmitted to the PLC control system, thereby forming a process pipeline system that short-circuits the boiler tube bundle and can control the economizer heating surface. The abbreviation WSC flue gas regulation process corresponds to Water Short Circuit Gas Temperature Regulating in English. The isolation and regulating valves are preferably electric stop valves. The pressure regulating bypass valve 15 and the pressure regulating bypass valve 28 are preferably self-operated pressure regulating valves. The control valve opening pressure is 1.55MPa. There are two sets of water-side bypass piping, which are arranged symmetrically on both sides of the boiler. A remote pressure transmitter is installed in front of the regulating valve three 4; the number of regulating valve four 6, regulating valve five 7, and pressure regulating bypass valve two 8 is the same as the number of economizer branches in the front end of the SCR catalyst, and a remote pressure transmitter is installed behind the regulating valve four 6; the outlet diameter of the pressure regulating bypass valve one 5 is not greater than DN50, and the outlet diameter of the pressure regulating bypass valve two 8 is not greater than DN15; the outlet pipeline of the 7# pressure regulating bypass valve is connected to the upper side or above the economizer collecting header 13; the first return elbow 18 on the economizer branch in the front end of the SCR catalyst at the outlet of the boiler economizer distribution header 12 should be partially exposed, and the insulation layer of the remaining return elbows 18 should be changed to soft rock wool insulation material with a density of 80kg / m3 and a thickness of not less than 100mm.

[0033] The utility model connects the return water of the heat network to the hot water boiler through the water-side bypass pipeline, and there is no need to modify the boiler water-cooled wall and the water-cooled wall ceiling, and has no effect on the furnace body; there is no need to lead out the hot flue gas pipeline to adjust the flue gas temperature, which can reduce the project cost; part of the flue gas is led out from in front of the flag-shaped tube heat collection surface, the amount of flue gas passing through the flag-shaped tube heat exchanger and the economizer is reduced, the heat exchange intensity is reduced, and mature and reliable steam-water valves are used, with low failure rate and low maintenance cost; there is no need to short-circuit the flue gas, which has little effect on the thermal efficiency of the boiler. At low load, although the heat absorption of the flag-shaped tube heating surface is greatly reduced, the tail economizer has an increased water flow rate, a lower water temperature, an increased temperature difference between the flue gas and water, and an increased heat absorption, which saves coal consumption compared with the short-circuit flue gas method.

Claims

1. A flue gas temperature regulating device for the convection heating surface at the rear of a WSC boiler, characterized in that: It includes a water-side bypass pipeline of a flag-tube heat exchanger, on which a valve group, a regulating valve 1, a regulating valve 2 and a regulating valve 3 are arranged. One end of the regulating valve 1 is connected to the inlet of the boiler water inlet header, the other end of the regulating valve 1 is respectively connected to the valve group and the regulating valve 2, the other end of the regulating valve 2 is respectively connected to the regulating valve 3, the outlet of the flag-tube upper header and the inlet of the economizer distribution header, and the water-side bypass pipeline is connected to the heat network return pipeline through the valve group.

2. A flue gas temperature regulating device for the rear convection heating surface of a WSC boiler according to claim 1, characterized in that: It also includes a regulating valve four and a regulating valve five. The outlet of the economizer distribution header is connected to the inlet of the economizer collection header through a number of branch pipes one. The flue gas flows through each branch pipe from left to right from the side. The SCR reactor is arranged in the gap in the middle of the branch pipe bundle. An SCR catalyst is arranged in the SCR reactor. Each branch pipe one arranged upstream of the flue gas of the SCR reactor is provided with a corresponding regulating valve four at a position close to the economizer distribution header, and each branch pipe one close to the economizer collection header is provided with a corresponding regulating valve five.

3. The flue gas temperature regulating device for the tail convection heating surface of a WSC boiler according to claim 1, characterized in that: The valve group is a cut-off valve and a check valve connected in series, and a pressure regulating bypass valve 1 is arranged at the outlet of the regulating valve 3.

4. A flue gas temperature regulating device for the rear convection heating surface of a WSC boiler according to claim 2, characterized in that: A pressure regulating bypass valve 2 is provided at the inlet of the regulating valve 5, the flag tube upper header is used to collect the hot water of the flag tube bundle, the economizer distribution header is used to distribute the hot water from the flag tube upper header to the economizer tube bundle, and the economizer collection header collects the hot water from the economizer tube bundle.

5. The flue gas temperature regulating device for the tail convection heating surface of a WSC boiler according to claim 1, characterized in that: It also includes temperature sensors and pressure sensors. There are several temperature sensors and pressure sensors, which are used to detect the temperatures of the inlet flue gas duct of the boiler water inlet header, the inlet flue gas duct of the economizer distribution header, the front end of the SCR catalyst, and the economizer branch pipe arm. The pressure sensors are used to detect the valve front pressure of the regulating valve three and the valve front pressure of the regulating valve four.

6. The flue gas temperature regulating device for the tail convection heating surface of a WSC boiler according to claim 1, characterized in that: The flag tube heat exchanger consists of a boiler water inlet header, a flag tube upper header, and a flag tube bundle connected between the boiler water inlet header and the flag tube upper header.

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